NPPB and chronic obstructive pulmonary disease: However, RAP (P = 0.003), PAOP (P = 0.007; Table 4) and serum NT-proBNP levels decreased only in the COPD group [162 (22.6–302.3) to 100.8 (43.9–131) pg/ml, P = 0.042; Fig. 3b].